A geared motor assembly configured so as to output the output rotation of a motor via a reducer having high transmission precision is used in a drive component requiring a high degree of positioning precision in an industrial robot, a machine tool, or the like. As disclosed in Patent Document 1, a known example of such a geared motor assembly is a configuration in which the output shaft rotation of a reducer disposed on the front side of a motor is transferred to the rear side of the motor via a rotation-transmitting shaft disposed as being passed through a hollow part of a hollow motor shaft, and the rotation angle of the reducer output shaft is detected by an angle sensor disposed on the rear side of the motor.
Patent Documents 2 and 3 disclose configurations of a geared motor assembly in which a sleeve extending in the axial direction through the center of the assembly is provided, and the front end of the sleeve is connected to a rotation output member of a reducer.    [Patent Document 1] Japanese Laid-open Patent Application No. 2006-271189    [Patent Document 2] Japanese Laid-open Patent Application No. 2006-144971    [Patent Document 3] Japanese Laid-open Patent Application No. 2002-243000